Nitrogen Starvation Research Articles

Plasticity of Root System Architecture and Whole Transcriptome Responses Underlying Nitrogen Deficiency Tolerance Conferred by a Wild Emmer Wheat QTL.

Our aim was to elucidate mechanisms underlying nitrogen (N)-deficiency tolerance in bread wheat (cultivar Ruta), conferred by a wild emmer wheat QTL (WEW; IL99). We hypothesised that the tolerance in IL99 is driven by enhanced N-uptake through modification of root system architecture (RSA) underscored by transcriptome modifications. Severe N-deficiency (0.1 N for 26 days) triggered significantly higher plasticity in IL99 compared to Ruta by modifying 16 RSA traits; nine of which were IL99-specific. The change in root growth in IL99 was collectively characterised by a transition in root orientation from shallow to steep, increased root number and length, and denser networks, enabling nutrient acquisition from a larger volume and deeper soil layers. Gene ontology and KEGG-enrichment analyses highlighted IL99-specific pathways and candidate genes elevated under N-deficiency. This included Jasmonic acid metabolism, a key hormone mediating RSA plasticity (AOS1, TIFY, MTB2, MYC2), and lignification-mediated root strengthening (CYP73A, 4CL). 'N-metabolism' was identified as a main shared pathway to IL99 and Ruta, with enhanced nitrate uptake predominant in IL99 (NRT2.4), while remobilisation was the main strategy in Ruta (NRT2.3). These findings provide novel insights into wheat plasticity response underlying tolerance to N-deficiency and demonstrate the potential of WEW for improving N-uptake under suboptimal conditions.

The impact of nutrient deficiency on the structure of soil microbial communities within a double-cropping system

In the North China Plain, it is common for farmers to regularly clear crop residues from their fields. The prevalent practice of fertilization in this region continues to depend heavily on the use of compound fertilizers. Howere , long-term single fertilizer application has become the norm in the present agricultural production, which not only destroys the crop rotation system but also negatively affects the soil environment and crop yields. The current knowledge of how nutrient deficits affect the microbial community structure in double-cropping systems is still limited. To clarify the specific response of soil microorganisms to the absence of key nutrients in the ecosystems of the annual double cropping system, this study investigated how the lack of essential nutrients affected the diversity, abundance, and functional dynamics of microorganisms in the soil, and designed five treatment methods: (1) CK, nofertilizer treatment; (2) NPK, adequate nitrogen fertilizer, phosphorus fertilizer, and potassium fertilizer treatment; (3) PK, nitrogen deficiency treatment; (4) NK, phosphorus deficiency treatment; and (5) NP, potassium deficiency treatment. The results showed that in two growing seasons, NPK treatment increased the yields of wheat and corn by 16.9% and 27.0%, respectively, while NK and NP treatments increased by 13.4%, 5.4%, 25.0%, and 17.9%, respectively, and the total annual yield increased by 21.1%. In addition, NPK treatment promoted the microbial diversity and abundance of wheat and maize, and balanced fertilization provided more comprehensive nutritional support for crops. Compared to other nutrient-deficient treatments, NPK treatment substantially increased the abundance and functional diversity of soil bacterial and fungal communities (p<0.05). The structure and abundance of soil microbial communities are significantly correlated with soil physicochemical factors that involve organic matter, pH, potassium content, phosphorus, and nitrogen levels. pH is the primary environmental factor influencing the diversity of soil microbial communities.

Transcriptome-scale analysis uncovers conserved residues in the hydrophobic core of the bacterial RNA chaperone Hfq required for small regulatory RNA stability.

The RNA chaperone Hfq plays crucial roles in bacterial gene expression and is a major facilitator of small regulatory RNA (sRNA) action. The toroidal architecture of the Hfq hexamer presents three well-characterized surfaces that allow it to bind sRNAs to stabilize them and engage target transcripts. Hfq-interacting sRNAs are categorized into two classes based on the surfaces they use to bind Hfq. By characterizing a systematic alanine mutant library of Hfq to identify amino acid residues that impact survival of Escherichia coli experiencing nitrogen (N) starvation, we corroborated the important role of the three RNA-binding surfaces for Hfq function. We uncovered two, previously uncharacterized, conserved residues, V22 and G34, in the hydrophobic core of Hfq, to have a profound impact on Hfq's RNA-binding activity in vivo. Transcriptome-scale analysis revealed that V22A and G34A Hfq mutants cause widespread destabilization of both sRNA classes, to the same extent as seen in bacteria devoid of Hfq. However, the alanine substitutions at these residues resulted in only modest alteration in stability and structure of Hfq. We propose that V22 and G34 have impact on Hfq function, especially critical under cellular conditions when there is an increased demand for Hfq, such as N starvation.

The translation initiation factor eIF2 is phosphorylated to inhibit protein translation through reactive oxygen species under nutrient deficiencies in Arabidopsis

Nitrogen (N), phosphorus (P) or potassium (K) deficiency in plants can lead to a decrease in amino acid and protein synthesis. However, it is unknown how protein translation gets repressed during macronutrient deficiencies. Previous research has shown that general control non-depressible 1 (GCN1) cooperate with GCN2 to phosphorylate the alpha subunit of eukaryotic translation initiation factor (eIF2α). In this study, we observed phosphorylation of eIF2α under N, P, and K deficiencies, which was found to be lost in gcn1. Mutant gcn1 displayed higher sensitivity to macronutrient deficiencies compared to the wild-type (WT). The evidence of in situ reactive oxygen species (ROS) accumulation in leaves indicated that macronutrient starvation triggers ROS production. Treatment with Dimethylthiourea (DMTU), a ROS scavenger, eliminated ROS and reversed eIF2α phosphorylation induced by nutrient deficiency. Moreover, it was discovered that protein translation was reduced under N or K deficiency in the WT but not in gcn1, whereas under P deprivation, protein translation was reduced in both the WT and gcn1. We additionally found that DMTU can partially recover translation inhibition under N or K deprivation. Taken together, it is concluded that GCN1-GCN2-eIF2α pathway is regulated by ROS and is essential for plant survival under macronutrient starvation conditions.

Deciphering the impact of NOS-derived NO on nitrogen metabolism and carbon flux in the heterocytous cyanobacterium Aphanizomenon flos-aquae 2012/KM1/D3.

Nitric oxide synthases (NOSs) are heme-based monooxygenases that catalyze the NADPH-dependent oxidation of L-arginine to produce NO and L-citrulline. Over the past five years, the identification and characterization of NOS homologs in cyanobacteria have significantly advanced our understanding of these enzymes. However, the precise mechanisms through which NOS-derived NO influences nitrogen metabolism remain incompletely elucidated. Therefore, the present study aims to investigates the impact of NOS-derived NO on nitrogen metabolism, heterocyte development, and carbon utilization dynamics in Aphanizomenon flos-aquae. Results demonstrate a three-fold increase in NOS-dependent NO production during the log to stationary growth phase in reponse to L-arginine availability. This increase in NOS activity substantially impacted critical cellular processes related to nitrogen metabolism. Specifically, the inhibition of NOS activity disrupted regulatory mechanisms involving ntcA and glnB genes, resulting in a failure to induce hetR, hep, dev and nif genes necessary for heterocyte differentiation and nitrogenase synthesis. NOS-derived NO also played a pivotal role in modulating the glutamine synthetase-glutamate synthase (GS-GOGAT) pathway, as evidenced by the sharp decline in glutamine and glutamate levels under NOS inhibition, which indicates impaired nitrogen assimilation. Besides, the observed alterations in succinate, fumarate, malate and pyruvate suggest regulatory roles of NOS in energy metabolism. NOS-inhibited cells redirected carbon flux towards glycogen/lipid biosynthesis, alongside protein degradation causing chlorosis, indicating nitrogen deficiency and compromised cellular viability. In contrast, NOS elicitation enhanced metabolic activity, supporting nitrogen assimilation and cellular growth. Overall, our results revealed the complex relationship among NOS-derived NO signaling, nitrogen metabolism, and carbon flux in cyanobacteria.

Cloning of PgPP2C2 gene and analysis of its expression in response to nitrogen and phosphorus deficiency, and exogenous GR24 treatment in panax ginseng

Cloning of PgPP2C2 gene and analysis of its expression in response to nitrogen and phosphorus deficiency, and exogenous GR24 treatment in panax ginseng

Comparative metabolomic analysis of Haematococcus pluvialis during hyperaccumulation of astaxanthin under the high salinity and nitrogen deficiency conditions.

Revealing the differences of metabolite profiles of H. pluvialis during hyperaccumulation of astaxanthin under the high salinity and nitrogen deficiency conditions was the key issues of the present study. To investigate the optimum NaCl and NaNO3 concentration and the corresponding metabolic characteristic related to the astaxanthin accumulation in H. pluvialis, a batch culture experiment was conducted. The results indicated that 7.5g·L- 1 and 0g·L- 1 (nitrogen deficiency) were the optimum NaCl and NaNO3 levels for the astaxanthin accumulation respectively, under which the highest astaxanthin contents reached up to 7.51mg·L- 1 and 5.60mg·L- 1. A total of 132 metabolites were identified using LC-MS/MS technique, among which 30 differential metabolites with statistical significance were highlighted. Subsequently, 18 and 10 differential metabolic pathways in the high salinity (HS) and nitrogen-deficient (ND) treatments were extracted and annotated respectively. The values of Fv/Fm, Yield and NPQ were all at the highest level in the ND group during the experiment. The levels of the metabolites in the ND group were almost lower than those both in the control (CK) and HS group, while which in the HS group were substantially at the higher or close levels compared to the CK group. Finally, 7 metabolic markers related to the astaxanthin accumulation were highlighted in the HS and ND group respectively. L-Proline, L-Aspartate, Uridine 5'-monophosphate (UMP), Succinate, L-2-Hydroxygluterate, L-Valine and Inosine 5'-monophosphate (IMP) were identified as the metabolic markers in the HS group, whose fold change were 0.85, 4.14, 0.31, 0.66, 3.10, 1.32 and 0.30. Otherwise, the metabolic markers were Glyceric acid, Thymine, sn-Glycerol 3-phosphate, Glycine, Allantoic acid, L-Valine and IMP in the ND group, with the fold change 0.23, 2.11, 0.38, 0.41, 0.50 and 2.96 respectively. The results provided the comparative metabolomic view of astaxanthin accumulation in H. pluvialis under the different cultivation conditions, moreover showed a novel insights into the astaxanthin production.

Integrated transcriptomics and metabolomics analyses provide new insights into cassava in response to nitrogen deficiency.

Nitrogen deficiency is a key constraint on crop yield. Cassava, the world's sixth-largest food crop and a crucial source of feed and industrial materials, can thrive in marginal soils, yet its yield is still significantly affected by limited nitrogen availability. Investigating cassava's response mechanisms to nitrogen scarcity is therefore essential for advancing molecular breeding and identifying nitrogen-efficient varieties. This research undertook a comprehensive analysis of cassava seedlings' physiological, gene expression, and metabolite responses under low nitrogen stress. Findings revealed that nitrogen deficiency drastically suppressed seedling growth, significantly reduced nitrate and ammonium transport to aerial parts, and led to a marked increase in carbohydrate, reactive oxygen species, and ammonium ion levels in the leaves. Transcriptomic and metabolomic analyses further demonstrated notable alterations in genes and metabolites linked to carbon and nitrogen metabolism, flavonoid biosynthesis, and the purine metabolic pathway. Additionally, several transcription factors associated with cassava flavonoid biosynthesis under nitrogen-deficient conditions were identified. Overall, this study offers fresh insights and valuable genetic resources for unraveling cassava's adaptive mechanisms to nitrogen deprivation.

From Practice to Science: Assessment Soil Nutrient Status Using “Minus One Element Technique (MOET)” for Early Growth of Maize

Soil nutrient deficiency will influence maize growth, so it is necessary to add nutrients based on the fertility status of the soil. One way to find out the nutrient soil status using a simple method is using the minus one element technique (MOET). The minus one element technique (MOET) determines which element is the limiting factor. This study was carried out to confirm the nutrient soil status using the minus one element technique (MOET) with the early growth of maize as the indicator. The research was conducted in greenhouse, Polytechnic of Lamandau, Central Borneo, Indonesia, at an altitude of 50 m above sea level. The research used a non-factorial design arranged in a completely randomized block design and five fertilizer treatments based on the minus one element technique consisting of control (without fertilization), PK, NP, NK, and NPK with three replications. The results showed that the deficiency of nitrogen, potassium, and phosphorus reduced the growth of maize, leaf greenness, photosynthetic rate, and especially the total dry weight of the plant. The dry weight of maize roots decreased by 18.85% - 75.47% when N, P, and K fertilizer were not applied. Then the decrease in photosynthesis rate ranged from 18.23% to 46.21% when N, P, and K fertilizer were not applied. The low of photosynthesis rates resulted in the accumulation of plant dry weight was hampered, and there was a decrease of 8.00% -74.43%. The results of the evaluation of fertility status are based on the results of the relative dry weight of the plant, which was

Foliar application of nitrates limits lead uptake by Cucumis sativus L. plants.

Lead is a toxic heavy metal, which accumulates in the soil and is readily absorbed by plant roots. The uptake of toxic elements by crops is a serious threat to human health. For this reason, it is important to prevent the incorporation of heavy metals into the food chain. Our previous study showed that foliar application of calcium nitrate reduces the intensity of lead uptake by different plant species. A significant decrease in metal concentration was observed both in the roots and in the shoots of three crops: tomato, cucumber, and flax. The present research investigated the mechanism for limiting lead accumulation in plant tissues. The experiments were conducted on Cucumis sativus L. seedlings, grown in hydroponic conditions. To compare the role of Ca2 + and NO3- ions in the restriction of lead uptake three different calcium salts (nitrate, chloride, and formate), and two nitrates (calcium and potassium) were applied foliarly to plants. The results show that Ca(NO3)2 is more efficient in decreasing lead accumulation in tissues than other calcium salts which suggests an important role of NO3- ions in the process. In addition, the study demonstrated that the exogenous supply of nitrates helps compensate for nitrogen deficiency caused by lead action and supports the mineral balance. The reduction in lead toxicity to plants after foliar application of nitrates may be due to the stimulation of the biosynthesis of nitric oxide - a key molecule responsible for stress response.

Effect of different nutritional materials on laccase activity and biomass accumulation of the Auricularia cornea var. Li strain

The laccase activity changes of the Auricularia cornea var. Li strain were studied over a continuous 9-day period using different carbon sources, nitrogen sources, and lignocellulose as liquid fermentation inducers. The results showed that the addition of carbon sources, nitrogen sources, and alkaline lignin all stimulated Auricularia cornea var. Li to secrete laccase and promoted the accumulation of mycelial biomass. Both carbon and nitrogen deficiencies could stimulate Auricularia cornea var. Li to produce more laccase, but they were detrimental to the accumulation of mycelial biomass. Maltose and peptone should be prioritized as materials for cultivating high-laccase-producing Auricularia cornea var. Li strains through liquid fermentation. Lignocellulosic biomass could significantly enhance laccase activity in Auricularia cornea var. Li. During the cultivation of Auricularia cornea var. Li., wheat bran and cottonseed hulls that produced high levels of laccase should be recommended. This study partially revealed the laccase production characteristics of Auricularia cornea var. Li and identified culture substances that were beneficial for laccase secretion during different growth stages of the mushroom. The results provide a foundation for improving the yield and quality of Auricularia cornea var. Li.

Geospatial techniques-based land suitability analysis for sustainable production of major crops in Sile Watershed of Gamo Zone, Southern Ethiopia.

Crop farming by smallholder farmers of Ethiopia and Sile Watershed is practiced based on commonsense experiences of farmers. This study was targeted to evaluate the suitability of land for the production of four major crops in Sile Watershed. Data were acquired from sources such as climate data (from CHRS data portal CRU TSv.4.05), slope (via Digital Elevation Model, ASTER 30m), and soil data via GPS-based survey, lab-test and others. Composite sampling was used to collect 43 soil samples (at 30cm depth) from the upstream (21), midstream (13) and downstream (9), and considering land use/cover classes. Requirements of the four crops were set using manuals and literature. Analytical Hierarchy Process was used to prioritize the multiple criteria used for assessment. The weighted overlay technique was used to analyze and map the suitability levels of the watershed for the four crops using ArcGIS. The results revealed that 51.7%, 41.7%, 42.2% and 35.4% of Sile watershed was 'highly suitable' for the sustainable production of maize, banana, teff and barley, respectively; however, 6.3 %, 27.6%, 16.3%, and 4.4% of the area was not suitable for the production of the respective crops. While the land suitability of maize and banana is confined to the downstream and partly the midstream, the high suitability of barley is limited to the upstream. Nitrogen, phosphorous, organic carbon, soil pH and salinity showed negative correlation with altitude and rainfall at 99% and 95% confidence levels. Variable rainfall, salinity and alkalinity are the main constraints of the four crops in the downstream. But slope steepness, organic carbon, phosphorous and nitrogen deficiencies, and soil acidity are the main threats of yield in the upstream and partly the midstream. Thus, stakeholders should be coordinated to apply agronomic, irrigation, structural and vegetative measures for tackling the productivity bottlenecks of Sile watershed, Southern Ethiopia.

Nitrogen stress-induced modulation of antimicrobial and antioxidant activities in Aphanothece sp.: Insights from phytochemical profiling and molecular docking

The modulation of nutrient availability represents a critical factor influencing the metabolic pathways and production of bioactive compounds in algae. This study aimed to examine the impact of nitrogen stress on the antimicrobial and antioxidant properties, phytochemical composition, and molecular docking assessments of the cyanobacterium Aphanothece sp. The results demonstrated that Aphanothece sp. when cultivated under conditions of nitrogen deficiency, exhibited markedly elevated antimicrobial and antioxidant activity compared to the control. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of the extracts obtained from algae on E. coli ATCC 25922 were found to be 25 mg mL−1 when the sample was grown in nitrogen medium and 6.25 mg mL−1 when grown in a nitrogen-free medium. The IC50 value obtained from DPPH free radical scavenging assay changed from 137.30 ± 16.22 mg mL−1 to 20.07 ± 1.55 mg mL−1 in nitrogen-free medium. According to the results of GC–MS analysis, the major components in the extract obtained from the algae grown in the nitrogen-free environment were 13,16-Octadecadiynoic acid, methyl ester (35.10 %) and Hexadecanoic acid, methyl ester (22.65 %), while the major components in the extract obtained from the algae grown in nitrogen-containing medium were Protopine (65.68 %) and 3,6,9,12,15-Pentaoxabicyclo(15.3.1)henicosa-1(21),17,19-triene-2,16-dione (12.15 %). The findings suggest a range of binding energies and interaction profiles for the compounds in the extracts with their molecular targets, which may have implications for their potential significance in therapeutic applications. The results of this study indicate that nitrogen stress can be employed as a strategic tool to enhance the production of valuable bioactive compounds in Aphanothece sp., thereby underscoring its potential applications in biotechnology and drug development.

Identification and Characterization of Key Genes for Nitrogen Utilization from Saccharum spontaneum Sub-Genome in Modern Sugarcane Cultivar.

Sugarcane (Saccharum spp.) is globally considered an important crop for sugar and biofuel production. During sugarcane production, the heavy reliance on chemical nitrogen fertilizer has resulted in low nitrogen use efficiency (NUE) and high loss. Up until now, there has been extensive research on the transcriptomic dynamics during sugarcane response to low nitrogen (LN) stress. However, the specific contribution of S. spontaneum to the NUE of modern sugarcane remains unclear. In the present study, the comparative transcriptome analysis of two contrasting sugarcane cultivars in response to nitrogen deficiency was performed via the combination of genomes of S. spontaneum and S. officinarum. Sub-genome analysis indicated that S. spontaneum supports the high NUE of modern sugarcane by providing genes related to nitrogen and carbohydrate metabolism, photosynthesis, and amino acid metabolism. Additionally, the key genes involved in nitrogen metabolism from the S. spontaneum were successfully identified through weighted gene co-expression network analyses (WGCNA), and a high-affinity nitrate transporter named ScNRT2.3 was subsequently cloned. Heterogeneous expression of the ScNRT2.3, a cell membrane-localized protein, could enhance the growth of Arabidopsis under low nitrate conditions. Furthermore, a conserved protein module known as NAR2.1/NRT2.3 was shown to regulate the response to LN stress in sugarcane roots through molecular interaction. This work helps to clarify the contribution of S. spontaneum to the NUE in modern sugarcane, and the function of the ScNRT2.3 in sugarcane.

Revealing systematic changes in the transcriptome during the transition from exponential growth to stationary phase.

Nutrient limitations are critical environmental perturbations in bacterial physiology. Despite its importance, a detailed understanding of how bacterial transcriptomes are adjusted has been limited. By utilizing independent component analysis (ICA) to decompose transcriptome data, this study reveals key regulatory events that enable bacteria to adapt to nutrient limitations. The findings not only highlight common responses, such as the stringent response, but also condition-specific regulatory shifts associated with carbon, nitrogen, and sulfur starvation. The insights gained from this work advance our knowledge of bacterial physiology, gene regulation, and metabolic adaptation.

Phlomoides rotata adapts to low-nitrogen environments by promoting root growth and increasing root organic acid exudate

Nitrogen (N) is one of the three major elements required for plant growth and development. It is of great significance to study the effects of different nitrogen application levels on the growth and root exudates of Phlomoides rotata, and can provide a theoretical basis for its scientific application of fertilizer to increase production. In this study, Phlomoides rotata were grown under different nitrogen conditions for two months. Soil and plant analyzer development (SPAD) values, bioaccumulation, root morphology, root exudate composition, nitrogen metabolism enzyme and antioxidant enzyme activity were evaluated. The results showed that compared with CK (no N fertilizer), N2 (CO(NH2)2 80 mg/kg) and N3 (CO(NH2)2 160 mg/kg) through significantly improved the activities of nitrogen metabolism enzyme nitrite reductase (NiR), glutamate dehydrogenase (GDH) and glutamine synthetase (GS), enhanced the nitrogen metabolism process, and increased the accumulation of plant soluble sugars (SS) and soluble protein (SP), thus improving Phlomoides rotata biomass yield. After 60 days of treatment, low nitrogen (N1, CO(NH2)2 40 mg/kg) increased root length, root volume, root surface area, average root diameter, significantly increased the diversity of organic acids in root exudates, and enhanced the activity of antioxidant enzymes to adapt the nitrogen deficiency environment. This study can provide new ideas for understanding the mechanism of nitrogen tolerance in Phlomoides rotata and developing scientific fertilization management strategies for plateau plants and medicinal plants.

Accumulation of Carotenoid and Lipid in Microalgae Dunaliella bardawil DCCBC 15 Cultivated under Nitrogen Starved Conditions

Dunaliella bardawil is a unicellular green microalgae that can accumulate large amounts of carotenoids under adverse culture conditions, so it has high commercial value and is used as a functional food. Nutrient starvation, especially nitrogen starvation, induces carotenoid and lipid production in algal cells. Dunaliella bardawil cells were grown in MD4 medium after 12 cultural days reaching maximum cell density (1,4x106 cells/mL) that changed to four stress conditions—nitrogen replete, nutrient starvation, and half and fully nitrogen-depleted conditions—to investigate the carotenoid and lipid contents of D. bardawil microalgae. The results showed that the cell density D. bardawil decreased significantly under cultural conditions. High amounts of carotenoids were detected under fully nitrogen-depleted conditions (14.631 pg/cell; car/chl: 12.346). D. bardawil was able to overproduce lipids under both nitrogen-free (351.580 pg/cell; lipid/chl: 219.792) and fully nitrogen-free (373.136 pg/cell; lipid/chl 321.401) conditions. Therefore, fully nitrogen-depleted conditions of cultivation stimulate significantly D. bardawil cells accumulating a large amounts lipid and carotenoid.

Proteomic and phosphoproteomic analyses reveal that TORC1 is reactivated by pheromone signaling during sexual reproduction in fission yeast.

Starvation, which is associated with inactivation of the growth-promoting TOR complex 1 (TORC1), is a strong environmental signal for cell differentiation. In the fission yeast Schizosaccharomyces pombe, nitrogen starvation has distinct physiological consequences depending on the presence of mating partners. In their absence, cells enter quiescence, and TORC1 inactivation prolongs their life. In presence of compatible mates, TORC1 inactivation is essential for sexual differentiation. Gametes engage in paracrine pheromone signaling, grow towards each other, fuse to form the diploid zygote, and form resistant, haploid spore progenies. To understand the signaling changes in the proteome and phospho-proteome during sexual reproduction, we developed cell synchronization strategies and present (phospho-)proteomic data sets that dissect pheromone from starvation signals over the sexual differentiation and cell-cell fusion processes. Unexpectedly, these data sets reveal phosphorylation of ribosomal protein S6 during sexual development, which we establish requires TORC1 activity. We demonstrate that TORC1 is re-activated by pheromone signaling, in a manner that does not require autophagy. Mutants with low TORC1 re-activation exhibit compromised mating and poorly viable spores. Thus, while inactivated to initiate the mating process, TORC1 is reactivated by pheromone signaling in starved cells to support sexual reproduction.

Bicarbonate and nitrogen starvation: A dynamic duo for canthaxanthin accumulation in Chlorella saccharophila

Bicarbonate and nitrogen starvation: A dynamic duo for canthaxanthin accumulation in Chlorella saccharophila

Macronucleophagy maintains cell viability under nitrogen starvation by modulating micronucleophagy

Lysosome/vacuole-mediated intracellular degradation pathways, collectively known as autophagy, play crucial roles in the maintenance and regulation of various cellular functions. However, little is known about the relationship between different modes of autophagy. In the budding yeast Saccharomyces cerevisiae, nitrogen starvation triggers both macronucleophagy and micronucleophagy, in which nuclear components are degraded via macroautophagy and microautophagy, respectively. We previously revealed that Atg39-mediated macronucleophagy is important for cell survival under nitrogen starvation; however, the underlying mechanism remains unknown. Here, we reveal that defective Atg39-mediated macronucleophagy leads to the hyperactivation of micronucleophagy, resulting in the excessive transport of various nuclear components into the vacuole. Micronucleophagy occurs at the nucleus–vacuole junction (NVJ). We show that nuclear membrane proteins localized to the NVJ, including Nvj1, which is responsible for micronucleophagy, are degraded via macronucleophagy. Therefore, defective Atg39-mediated macronucleophagy results in the accumulation of Nvj1, which contributes to micronucleophagy enhancement. Blocking micronucleophagy almost completely suppresses cell death caused by the absence of Atg39, whereas enhanced micronucleophagy correlates with death in Atg39-mutant cells under nitrogen starvation. These results suggest that macronucleophagy modulates micronucleophagy in order to prevent the excess removal of nuclear components, thereby maintaining nuclear and cellular homeostasis during nitrogen starvation.